Architecture / June 19, 2018 / .
Clients who prioritise cost over speed or who require fixed price lump sums will generally experience longer development programmes, as designs must be substantially completed before tenders can be obtained. This process may take a considerable amount of time as careful thought is required to develop and refine the scheme design. The design, in turn, influences the contractors construction methods which determine length of time taken to complete the contract on site.
The site topography i.e. the natural site features, ground conditions and obstructions, existing and adjoining building, and underground and over-ground services all impact on how the building is designed and subsequently constructed. The nature of each site must be individually checked to establish potential problems. Greenfield developments cost less than brownfield sites which may incur significant demolition, site clearance and remediation costs. Heavily sloped sites require extensive stepping or cut and fill operations and such sites may be dangerous and adversely affect the working conditions and productivity of operatives and plant output. Sites with poor loadbearing capacity will require more expensive foundations while exposed or waterlogged sites will also reduce overall productivity. The cost of dealing with unforeseen ground conditions, archaeological finds and encountering uncharted buried services may be substantial and will be borne by either the client or contractor, depending on the form of contract employed.
It is clear that the purpose of a building will have a major bearing on its cost. Housing has a very different cost range to apartments and commercial development. Likewish the cost of providing public amenities such as conference centres, theatres and sports stadia cannot be directly related to the provision of public infrastructure such as hospitals or schools. The cost of each building must be related to its individual design, which may be benchmarked against similar national and international projects.
This is where the contractor provides the design and construction under one contract. Turnkey projects and many public private partnership developments are examples of this approach. Design and build offers the client competitively priced projects completed within rapid time frames by enabling the contractor to value manage the employers requirements and overlap design and construction operations. It is not successful where the employers requirements are poorly defined and the approach tends to produce functional architecture in terms of appearance.